1. Field of the Invention
The present invention relates to a self-localization technology when a movable body mounted with a camera self-localizes.
2. Description of the Related Art
Various devices that estimate a self-location of a movable body based on information acquired from sensors including internal sensors such as a rotary encoder and a gyro sensor and external sensors such as a camera and a laser distance sensor mounted on the movable body such as a robot or a vehicle have been proposed. A technique to estimate a relative self-location from a reference point by adding up moving amounts of a movable body acquired by an internal sensor such as a rotary encoder or a gyro sensor is called dead reckoning and is superior in real-time properties due to its low-load calculation processing, but a position error accumulates in accordance with the moving amount. On the other hand, a technique to estimate a self-location based on, after detecting features of a surrounding traveling environment as a landmark of the self-location using an external sensor such as a camera or a laser range finder, absolute positions of the features grasped by map matching is known and precision of position is thereby improved, but the calculation processing thereof is high-loaded. Therefore, the technique to use dead reckoning and the technique to use map matching are each a tradeoff between precision and processing loads and to realize high-precision self-localization at low processing load, various devices using dead reckoning and map matching complexly in a time sequence and further using satellite positioning including GPS (Global Positioning System) outdoors have been proposed.
For example, according to JP-2008-165275-A, a map of landmarks whose positions do not change is prepared and landmark candidates are detected by an external sensor such as a camera or a laser distance sensor. Because matching a landmark candidate to the map each time is a high processing load, the landmark candidate matched to the map last time and the current landmark candidate are associated to reduce the number of times of directly matching the current landmark candidate to the map.
For example, according to JP-2004-5593-A, environment information for self-localization is acquired and the acquired environment information is matched to environment information contained in map information to correct self-localization values based on matching results. For matching of the environment information to the environment information contained in map information, matching to the map is performed within a predetermined range that is present based on self-localization values and if correction information of the self-location is not obtained in the matching, matching to the map is performed again by increasing the predetermined range to avoid losing the self-location.